If your yard gets a lot of water during storms, rain gardens are a beautiful way to prevent runoff from causing oversaturation. Since rain gardens use native wetland plants, they can make an attractive, low-maintenance addition to your garden. Scout out your yard for an ideal rain garden spot, then dig a small basin to fill with compost and add your new plants. Once you've planted your rain garden, weed and mulch it routinely to keep your rain garden healthy.

Steps

Part 1

Choosing a Site

1

Position your garden at least 10 feet (3.0 meters) from your home. If your garden is too close to the house, water may erode at the home's foundation. This can cause basement flooding or structural problems.[1] Keep your rain garden away from driveways and sidewalks as well to avoid pathway erosion.[2]

Measure your area's slope. Using a long, straight wooden board and a carpenter's level, measure the slope of your projected area. To get enough rain water into your garden, you'll need a slope of at least 1 inch (2.54 centimeters) in 4-1/2 feet (1.32 meters), or 2%. Without this natural slope, you'll have to create it naturally by digging.[3]

Because rain gardens protect your yard from water overflow, you will want a slope of two percent or more.

3

Test the soil in your location. Before you begin digging, check the soil to make sure it's suitable for your garden. While rain gardens can thrive with less permeable soils like clay, they will do best with well-draining or sandy soils. Dig a shallow hole in your projected area and fill it with water. If the water remains in the hole for two days, the soil is not permeable enough for a rain garden.

If all the soil in your area is non-permeable, you can create suitable soil on your own. The ideal rain garden soil will be 30% sand, 30-40% loamy topsoil, and 30-40% organic matter. Till this mixture into existing soil for proper drainage.[4]

How large your rain garden will be depends on your area's weather patterns. If you experience a lot of rainfall, you'll want a larger garden. Even small gardens, however, will help with runoff.

5

Plan your garden's depth based on its slope. Rain gardens are usually between 4-8 inches (10.2-20.3 centimeters) deep. If your location's slope is less than 4%, you'll want a rain garden between 3-5 inches (7.6-12.7 centimeters) deep. For slopes between 5-7%, create a rain garden 6-7 inches (15.3-17.8 centimeters) deep. Slopes between 8-12% will be best at about 8 inches (20.3 centimeters) deep.[6]

Rain gardens deeper than 8 inches (20.3 centimeters), or with a slope over 12%, will not be ideal. They present a tripping hazard and generally hold water for too long, becoming more of a pond than a rain garden.

Part 2

Purchasing Plants

1

Choose plants native to your area. Plants that thrive well in rain gardens are hardy and healthy. Your rain garden will be most low-maintenance with regional plants because they will be adapted to the climate and local rainfall fluctuations.[7]

The best place to purchase native plants is at locally-owned plant nurseries.

2

Purchase perennial plants that have already matured. Younger plants will not thrive as well with high quantities of waters, so avoid buying seeds or seedlings. Their root systems are not developed enough to handle the downpour. Perennial plants last for several years, so plants at least one or two years old will have established root systems.

Look for plants that thrive well in wetlands. Choose plants that can handle lots of downpour. You can find native wetland plants via the U.S. Army Corps of Engineers National Wetland Plant List (NWPL) by visiting: http://wetland-plants.usace.army.mil/nwpl_static/index.html. You can also check local gardening magazines or your city's plant nursery to ask which wetland plants thrive in your climate.[8]

4

Add shrubs for erosion protection. Plants with dense root systems hold rain gardens together best. Shrubs generally have developed root systems that soak up excess water and prevent land erosion. Look for shrubs best adapted to your soil conditions. Most shrubs prefer well-draining soil to clays.[9]

Shrubs grow best in moist but not oversaturated conditions. Add several shrubs to rain gardens with especially excessive runoffs.[10]

Part 3

Building Your Garden

1

Dig out your garden area to the desired depth. Once you've staked out your rain garden dimensions and measured the slope, dig your garden to the desired depth. Even out your garden's bottom using the straight, flat board and carpenter's level. Continue measuring the garden's bottom until you've eradicated major bumps or dips.[11]

Build a berm to hold in water. A berm (or earthen dam) will prevent runoff from flowing out of your garden. Use leftover soil from digging to pack raised mounds of earth around the perimeter of the garden. Construct your berm with gentle sloping sides so it is less susceptible to erosion.[12]

3

Fill the basin with soil. After you've dug out your garden and added a berm, add soil to your rain garden. You can use pre-mixed rain garden soil, or you can use general gardening topsoil. Mix compost with your soil before adding it into your garden, as it will provide nutrients that may be lacking in the soil. Your soil's compost content should be around 20-30%.[13]

The clay content in your soil should be minimal. Take a handful of soil in your hand and squeeze it. If the soil stays clumped together and doesn't fall apart when prodded, your clay content is too high and you’ll need to amend the soil.

4

Add your chosen plants. Place your plants about one foot (0.3 meters) apart from each other so their roots have room to grow. A rain garden can have as little as three or as many as dozens of plants depending on your location's size.[14] Make sure to pack plenty of soil around the root systems to avoid drying out your plants.

Place shrubs in between flower varieties to bring out the colors between different plants and bring a stable root system to your garden.[15]

Some plant varieties may have specific planting instructions. Research the needs of each species to avoid damaging your plants.

Part 4

Maintaining Your Garden

1

Add mulch to your garden for the first two years. Mulch will keep the soil moist and helps nurture your plants while they adjust to the soil. Heavier mulches (like gorilla hair mulch and shredded wood or rock) are preferable in rain gardens to prevent them from floating away. A 2-3 inch (5-7.6 centimeters) layer covering the topsoil is preferred.[16]

After the second year, mulching is unnecessary but can be continued for aesthetic purposes.

2

Water your plants regularly, especially in dry spells. During the first few years or in periods of severe drought, you will need to water your garden in addition to the runoff it receives. Water your garden with about 1-2 inches (2.5-5 centimeters) per week. After several years, your plants will have fully established root systems and need less care. From then onward, only water your garden if it has not rained for 10 days (or if you notice signs of underwatering).[17]

Weed your garden regularly. For the first few years, your garden will be vulnerable to weeds so monitor your garden regularly. Remove weeds from the root to avoid regrowth. Once or twice a month is ideal to keep your plants healthy.[20]

After several years, your garden should be strong enough to handle itself beyond the occasional weed.

4

Inspect your garden often. Once a week, enter your rain garden and look for garden erosion or unhealthy plants. If any trash has washed into your rain garden, remove it along with any invading weeds. Check your garden several days after rain storms to make sure no standing water remains.[21]

If your rain garden has standing water for several days, your plants may become overhydrated. Add more organic mulch and topsoil to your rain garden to elevate the area and absorb the water quickly.

If your rain garden is under a downspout, make sure to clean your gutters regularly so that water can reach the plants.